metamorphic
Greenstone
Greenschist / Meta-basalt
Hardness: 6-7 (Mohs scale); Color: Dull green to dark grayish-green; Luster: Dull to waxy; Texture: Fine-grained, often massive or slightly foliated; Gravity: 2.8 - 3.2.
- Hardness
- 6-7 (Mohs scale)
- Color
- Dull green to dark grayish-green
- Luster
- Dull to waxy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Dull green to dark grayish-green; Luster: Dull to waxy; Texture: Fine-grained, often massive or slightly foliated; Gravity: 2.8 - 3.2.
Formation & geological history
Formed through the low-grade metamorphism of mafic igneous rocks like basalt or gabbro. This occurs at relatively low temperatures (300-450°C) and pressures in subduction zones or mountain-building regions.
Uses & applications
Historically used for making stone tools (axes/adzes); currently used as crushed stone for construction, decorative landscaping, and occasionally for carvings or lapidary work.
Geological facts
The green color comes from minerals like chlorite, epidote, and actinolite formed during metamorphism. In archeology, many 'celt' artifacts from the Neolithic era were crafted from varieties of greenstone.
Field identification & locations
Identify by its distinctive greenish hue and toughness. Often found in ancient volcanic belts or riverbeds as rounded cobbles. It is harder than most sedimentary rocks and will not scratch easily with steel.
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